1. Field of the Invention
The present invention relates to an apparatus and a method for handling reactor-internal equipments and, more particularly, an apparatus and a method for loading/unloading control rods, fuel supports, and control rod guide tubes into/from a boiling water reactor (referred to as xe2x80x9cBWRxe2x80x9d hereinafter).
2. Description of the Related Art
FIG. 10 is a fragmental sectional view showing a part of a reactor-internal structure of the BWR in an enlarged manner. As shown in FIG. 10, in the BWR, a core plate 3 is provided to a shroud 2 which is constructed integrally with a reactor pressure vessel (reactor vessel) 1. Control rod drive mechanism housings (referred to as xe2x80x9cCRD housingsxe2x80x9d hereinafter) 4 are provided to a bottom portion of the reactor pressure vessel 1 which is located at a lower portion of the core plate 3. A control rod drive mechanism (referred to as xe2x80x9cCRDxe2x80x9d hereinafter) 5 is installed inside the CRD housing 4.
A control rod guide tube (referred to as xe2x80x9cCRGTxe2x80x9d hereinafter) 6 is provided on the CRD housing 4. The CRGTs 6 are supported to be slightly protruded upwardly from the core plate 3. A fuel support(referred to as xe2x80x9cFSxe2x80x9d hereinafter) 8 is detachably attached to an upper opening portion of the CRGT 6. The CRGT 6 and the FS 8 are fixed by a positioning pin 11 which is provided on the core plate 3.
A control rod (referred to as xe2x80x9cCRxe2x80x9d hereinafter) 7 with a cruciform lateral sectional shape is provided in the CRGT 6 to be moved vertically. A bottom end of the CR 7 is coupled to a top end of the CRD 5. The CRs 7 can be inserted into clearances between the fuel assemblies 10 from top ends of the CRGTs 6 respectively.
A top portion of the FS 8 supports a bottom portion 15 of the fuel assembly 10. Also, a top portion 12 of the fuel assembly 10 is supported by an top guide 13 which is provided to the shroud 2.
FIG. 11 is a perspective view, partially omitted, showing an example of the CRGT 6 of the BWR. As shown in FIG. 11, a plurality of CRGT orifices 32 are formed on a top end side wall of the CRGT 6.
FIG. 12 is a perspective view showing an example of the FS 8 of the BWR. As shown in FIG. 12, a cruciform through hole 9 into which the CR 7 is inserted is formed in the FS 8. Four fuel assembly sustaining holes 31, which sustain four fuel assemblies 10 respectively, are formed on a top portion of the FS 8. In addition, a plurality of fuel support orifices (referred to as xe2x80x9cFS orificesxe2x80x9d hereinafter) 33 are formed on a bottom side surface of the FS 8.
FIG. 13 is a perspective view showing the fuel support with pin (referred to as xe2x80x9cPin-FSxe2x80x9d hereinafter) 22 of the BWR. The Pin-FSs 22 are provided to support mimic fuel assemblies (not shown) arranged in a peripheral portion of the core. This Pin-FS 22 is constructed by adding a pin 53 to the FS 8 shown in FIG. 12.
Then, if the CRs 7 are exchanged in the periodical inspection, the CRs 7 must be exchanged after the fuel assemblies 10 and the FSs 8, which are positioned at an upper location than the CRS 7, have been removed. The fuel assemblies 10 are unloaded by a refueling machine (not shown) which is installed on an operation floor (not shown), and then the CRS 7 and the FSs 8 are unloaded to outside the reactor.
As an equipment employed to execute unloading operations of the CRs 7 and the FSs 8, a CR and FS grapple (not shown) which can grasp the handle 7a of the CR 7 and the FS 8 at the same time has been proposed. After the CRs 7 and the FSs 8 have been unloaded from the reactor by the CR and FS grapple, the exchanging operation of the CRs 7 can be performed.
In addition, there is a rare case where the CRGTs 6 must be removed. In this case, such CRGTs 6 can be removed by a CRGT grapple (not shown).
However, in the event that the unloading operations of all the CRs 7, the FSs 8, and the CRGTs 6 from the reactor and the installing operations of them into the reactor must be performed in the periodical inspection or in the preventive maintenance, etc., there have been such problems that, if the CR and FS grapple and the CRGT grapple, for example, are employed, a time required for such operations is extremely prolonged and thus an exposure dose of the operator is increased correspondingly. Further, there has been such a problem that, if the CRs 7, the FSs 8, and the CRGTs 6 are unloaded from the reactor separately, it is difficult to secure respective storage spaces for them.
Therefore, it is an object of the present invention to provide a reactor-internal equipment handling apparatus and method capable of reducing a term of work which is needed for operations to load/unload control rods, fuel supports, and control rod guide tubes.
In order to achieve the object, according to the present invention, there is provided a reactor-internal equipment handling apparatus comprising: control rod holding means for releasably holding a control rod which is loaded in a reactor vessel; fuel support/control rod guide tube holding means for releasably holding both a fuel support, which supports a bottom end of a fuel assembly, and a control rod guide tube, on which the fuel support is placed at top end; and a main body frame to which both the control rod holding means and the fuel support/control rod guide tube holding means are fitted and is adapted to be hung down inside the reactor vessel.
Preferably, in the reactor-internal equipment handling apparatus, the fuel support/control rod guide tube holding means includes an orifice engaging member which is adapted to engage edge portions of orifices formed in the fuel support and the control rod guide tube, an orifice engaging member linking mechanism for manipulating the orifice engaging member, and orifice engaging member driving means for driving the orifice engaging member linking mechanism.
Preferably, the reactor-internal equipment handling apparatus further comprises a stroke varying mechanism for varying an operating stroke of the orifice engaging member linking mechanism; wherein an amount of motion of the orifice engaging member is adjusted by changing the operating stroke of the orifice engaging member linking mechanism by the stroke varying mechanism such that the orifice engaging member engages only the edge portion of the orifice formed in the fuel support.
Preferably, in the reactor-internal equipment handling apparatus, the orifice engaging member has stepped portions which come into contact with the edge portions of the orifices formed in the fuel support and the control rod guide tube, and
wherein the orifice engaging member linking mechanism is constructed to disable a motion of the orifice engaging member in a situation that the stepped portion of the orifice engaging member comes into contact with the edge portion of the orifice.
Preferably, in the reactor-internal equipment handling apparatus, the control rod holding means has a handle engaging member which is swingable and holds a hoisting handle provided on a top end of the control rod, and handle engaging member driving means for driving the handle engaging member to swing, and wherein the handle engaging member is formed of a hook member, and an own weight of the control rod is applied to hold a engaged state of the hoisting handle by the handle engaging member in a situation that the control rod holding means hoists the control rod via the handle engaging member.
Preferably, in the reactor-internal equipment handling apparatus, the control rod holding means and the fuel support/control rod guide tube holding means are fitted to the main body frame such that these means can be relatively displaced mutually along a longitudinal direction of the control rod, and both the fuel support and the control rod guide tube are hoisted after the control rod is slightly hoisted.
Preferably, the reactor-internal equipment handling apparatus further comprises a holding state detecting mechanism for detecting both a holding state of the control rod holding means about the control rod and a holding state of the fuel support/control rod guide tube holding means about the fuel support and the control rod guide tube; and a positioning state detecting mechanism for detecting a positioning state of the main body frame in the reactor vessel.
Preferably, in the reactor-internal equipment handling apparatus, the holding state detecting mechanism has a holding state confirming indicator lamp whose lighting state is changed depending upon a change in the holding states of the control rod holding means and the fuel support/control rod guide tube holding means, and the positioning state detecting mechanism has a positioning state confirming indicator lamp whose lighting state is changed depending upon a change in the positioning state of the main body frame in the reactor vessel.
Preferably, in the reactor-internal equipment handling apparatus, the positioning state detecting mechanism further includes a motion limiting mechanism for limiting a motion of the fuel support/control rod guide tube holding means when the main body frame is not properly placed at a predetermined position in the reactor vessel.
Preferably, the reactor-internal equipment handling apparatus further comprises a motion limiting mechanism locking device for making the motion limiting mechanism inoperative temporarily.
In order to achieve the object, according to the present invention there is provided a reactor-internal equipment handling method of loading/unloading equipment into/from a reactor vessel with a reactor-internal equipment handling apparatus comprising: control rod holding means for releasably holding a control rod which is loaded in a reactor vessel, fuel support/control rod guide tube holding means for releasably holding both a fuel support, which supports a bottom end of a fuel assembly, and a control rod guide tube, on which the fuel support is placed at a top end, a main body frame to which both the control rod holding means and the fuel support/control rod guide tube holding means are fitted and adapted to be hung down inside the reactor vessel, a holding state detecting mechanism for detecting both a holding state of the control rod holding means about the control rod, and a holding state of the fuel support/control rod guide tube holding means about the fuel support and the control rod guide tube, and a position state detecting mechanism for detecting a positioning state of the main body frame in the reactor vessel, the method comprising: detecting a positioning state of the main body frame in the reactor vessel with the positioning state detecting mechanism in order to confirm that the main body frame is properly positioned; holding the control rod by the control rod holding means and also holding both the fuel support and the control rod guide tube with the fuel support/control rod guide tube holding means; detecting, with the holding state detecting mechanism, both a holding state of the control rod holding means about the control rod and a holding state of the fuel support/control rod guide tube holding means about the fuel support and the control rod guide tube, to confirm that the control rod holding means holds the control rod and the fuel support/control rod guide tube holding means holds the fuel support and the control rod guide tube; and hoisting the main body frame by a fuel exchanger and simultaneously loading or unloading all of the control rod, the fuel support, and the control rod guide tube into or from the reactor vessel.
Preferably, in the reactor-internal equipment handling method the fuel support/control rod guide tube holding means includes an orifice engaging member which is adapted to engage edge portions of orifices formed in the fuel support and the control rod guide tube, an orifice engaging member linking mechanism for manipulating the orifice engaging member, and orifice engaging member driving means for driving the orifice engaging member linking mechanism, and wherein the orifice engaging member is simultaneously brought into contact with the edge portions of the orifices formed in the fuel support and the control rod guide tube.